what do you think would happen if I covered poured sugar with fondant? Trying to make a large base that will be able to take some weight. Thanks

I recently placed a fondant cut-out between 2 poured sugar disks. It seemed fine for about a week, then sugar started getting sticky and the fondant cut-out started breaking down.

You can build a VERY strong base out of pastillage... made right, pastillage can hold a surprising amount of weight.